1. Field of the Invention
The present invention generally relates to multi-cylinder internal combustion engines having a plurality of cylinders arranged in an array. In particular, the present invention relates to an improved crankshaft bearing structure suitable for an internal combustion engine equipped with a multilink-type piston-crank mechanism.
2. Background Information
Most internal combustion engines used in vehicles have a plurality of cylinders with a piston reciprocating in each of the cylinder and a crankshaft that is linked to the pistons by a piston-crank linking mechanism. Some internal combustion engines use a multilink-type piston-crank mechanism in which upper links are connected to piston pins of the pistons and lower links connect the upper links to crankpins of the crankshaft. One example of a multilink-type piston-crank mechanism is disclosed in Japanese Unexamined Patent Application Publication No. 2002-61501. In this type of multilink-type piston-crank, when the piston-stroke characteristics change, an excessive force acts on specific crankshaft bearings as a result of inertia force exerted on the crank bearings from crank rotating systems, thus making it difficult to attain sufficient bearing strength.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved multilink-type piston-crank mechanism. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.